Ejector devices of this type comprise one or more ejectors containing one or more jets or nozzles arranged in sequence and through which an air flow is fed at high pressure. The compressed air is fed to the ejector via a compressed-air duct connected to a source of compressed air. The ejector is in flow communication with a space from where air is evacuated by suction into the flow of compressed air through the ejector via slits formed between the nozzles, or at the outlet of the individual jet. The evacuated space is, via an air suction duct, in flow communication with one or more gripping member, typically in the form of one or more suction cups.
The flow of compressed air to the ejector is adjustable by means of a valve arranged in the compressed-air duct and adapted to open and shut off the flow of compressed air, and, where appropriate, for partial restriction of the flow to the ejector. The valve may be associated with a control member that regulates the flow of compressed air in accordance with instructions in a working program, and/or in response to a detected negative pressure sensed by means of a pressure sensor that communicates with the air suction duct. In a maximally decentralized embodiment, each suction cup has one or more dedicated ejectors, valve units and control members.
In ejector devices of this type, it is previously known to arrange a function for active ventilation of the suction cup so as to enable detachment of the gripped object, thereby allowing short work cycles. Such ventilation functions usually comprise an electrically activated valve, which upon opening lets in atmospheric pressure or compressed air to the evacuated space under the suction cup.